Valveless pneumatic hammer

Abstract

A valveless pneumatic hammer comprises a hollow casing having a backhead assembly at one end and a bit assembly at the other, and a piston reciprocable in the casing. There is a chamber divider at the backhead end of the casing which co-operates with the piston for conducting fluid under pressure into alternate chambers, one at each piston end, for reciprocation of the piston. A chamber divider is located within the casing by a locating split ring which holds the chamber divider axially against the backhead assembly. The chamber divider also has a recess in the end thereof nearest the piston which together with a bore in this piston end, comprises the fluid chamber at this end of the casing.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is: 
     
       1. An elongated valveless pneumatic hammer assembly comprising: an elongated hollow casing;   a backhead assembly at one end of the casing;   a bit assembly at the other end of the casing, having a passage through the bit assembly passing out to the atmosphere at the other end of the assembly;   a chamber divider disposed in the backhead end of the casing having a control rod projecting into the casing, the innermost end of the divider being adapted to seal against a piston bore during a portion of piston movement in use;   a piston having a large bore in one end and a smaller concentric bore through the other end into the larger bore, the larger bore end being adapted to cooperate with the chamber divider end for the sealing of the larger bore, the piston being further adapted to reciprocate between two positions, the first position being with the smaller bore end against the bit assembly with the bit assembly sealing off the smaller bore and the larger piston bore sealed off by the chamber divider end, and the second position being with the piston displaced towards the backhead assembly, the larger bore unsealed and the chamber divider control rod within and sealing off the smaller bore, and with the bit assembly removed from the smaller bore; a first chamber with the piston in the first position, formed by an upper portion of the bit assembly, the inner wall of the casing and a lower portion of the piston;   a second chamber with the piston in the second position, formed by the larger bore of the piston and an annular recess in the chamber divider; a first fluid supply path through the backhead assembly, between the chamber divider walls and the casing wall, into at least one passage between the inner casing wall and the piston while the piston is in the first piston position and into the first chamber;   a second fluid supply path through the backhead assembly, between the chamber divider wall and inner casing wall, between the inner wall of the large bore of the piston and the outer wall of the control rod and into the second chamber; a first fluid exhaust path from the first chamber into the bit assembly passage with the piston in the second position and out into the atmosphere; and     a second fluid exhaust path from the second chamber through the smaller piston bore with the piston in its first position, into the bit assembly passage and out to the atmosphere.   
     
     
       2. A valveless pneumatic hammer as claimed in claim 1, in which the end portion of the larger piston bore is stepped inwardly, and the innermost end portion of the chamber divider is stepped outwardly, the stepped portions being co-operable for the selective sealing off of the larger piston bore from the outside thereof by the sliding movement of the chamber divider within the larger piston bore. 
     
     
       3. A valveless pneumatic hammer as claimed in claim 1 or 2 in which the chamber divider is located within the casing by a split ring fitted partially within a concentric annular recess in the casing and partially in a concentric annular step-like rebate in an inner edge portion of the chamber adjacent the casing wall, to retain the chamber divider axially against the backhead assembly. 
     
     
       4. A valveless pneumatic hammer as claimed in claim 1 or 2 in which the first fluid supply path includes a concentric annular recess in the casing wall in the region thereof opposite the large bore end of the piston, a concentric annular recess in the middle region of the piston, and a concentric annular recess in the casing wall at the region thereof opposite the small bore end of the piston. 
     
     
       5. A valveless pneumatic hammer as claimed in claim 4 in which the recesses in the casing are no deeper than any internal screw threading on the casing. 
     
     
       6. A valveless pneumatic hammer as claimed in claim 1 in which the bit assembly is moveable between two positions, the first in which the shaft thereof is wholly within the casing and the second in which a portion of the shaft extends from the casing end. 
     
     
       7. A valveless pneumatic hammer as claimed in claim 6 in which the piston is moveable to a third position in which the small bore end of the piston is in contact with the inner end of the bit assembly when the bit assembly is in its second position, and the large bore piston end has sealed off the first fluid supply path as well as the second fluid supply path, there being a fluid path from between the casing wall and chamber wall to the second chamber through an opening in the wall of the end region of the chamber divider. 
     
     
       8. A valveless pneumatic hammer as claimed in claim 7 in which the opening is an outwardly stepped portion of the chamber divider. 
     
     
       9. A valveless pneumatic hammer as claimed in claim 1 in which the control rod of the chamber divider has a passage therethrough communicating with a pressure valve at the backhead end of the divider, the valve being adapted to open when the operating fluid of the hammer is below a predetermined minimum. 
     
     
       10. A valveless pneumatic hammer assembly comprising: an elongated hollow casing having a wall;   a backhead assembly at one end of said casing;   a bit assembly at the other end of said casing, said bit assembly having a passage extending to atmosphere at one axial extremity of said assembly;   a chamber divider having a wall and disposed in the backhead end of said casing including a control rod having a wall projecting into said casing, the innermost end of said chamber divider being dimensioned and configured for sealing engagement with a bore;   a piston carried in said casing for reciprocating movement between first and second positions, said piston having a large bore in one end and a smaller coaxial bore through the other end thereof which communicates with said larger bore, said larger bore end being adapted to co-operate with said chamber divider end for sealing of said larger bore, said piston in said first position being disposed with the smaller bore end against said bit assembly with said bit assembly sealing off said smaller bore and said larger piston bore sealed off by said chamber divider end, and said piston in said second position being disposed with said piston displaced towards said backhead assembly, said larger bore unsealed and said chamber divider control rod within and sealing off said smaller bore, and with said bit assembly removed from said smaller bore;   said assembly having a first chamber defined therein with said piston disposed in said first position, formed by an upper portion of said bit assembly, the inner wall of said casing and a lower portion of said piston; a second chamber defined when said piston is in said second position, said second chamber being defined by said larger bore of said piston and an annular recess in said chamber divider;   said assembly having a first fluid supply path extending through said backhead assembly, between said chamber divider wall and said casing wall, into at least one passage between said casing wall and said piston when said piston is in said first piston position and into said first chamber;   said assembly having a second fluid supply path extending through said backhead assembly, between said chamber divider wall and said casing wall, between the inner face of said wall of said large bore of said piston and the outer face of said wall of said control rod and into said second chamber;   said assembly defining a first fluid exhaust path from said first chamber into said passage in said bit assembly with said piston in said second position and out into the atmosphere; and   said assembly defining a second fluid exhaust path from said second chamber through said smaller piston bore with said piston in said first position, into said passage in said bit assembly passage and out to atmosphere.   
     
     
       11. A valveless pneumatic hammer as claimed in claim 10, in which the free end portion of said larger piston bore is stepped, and the axially innermost end portion of said chamber divider is stepped, said stepped portions being co-operating for selective sealing off of said larger piston bore by sliding movement of said chamber divider within said larger piston bore. 
     
     
       12. A valveless pneumatic hammer as claimed in claim 11, in which said chamber divider is located within said casing by a split ring. 
     
     
       13. A valveless pneumatic hammer as claimed in claim 11, in which said casing includes a concentric annular recess in the inner face thereof in the region thereof opposite said large bore end of said piston and a concentric annular recess in the inner face thereof proximate to the axial center of said piston, and a concentric annular recess in the inner face thereof opposite said smaller bore end of said piston. 
     
     
       14. A valveless pneumatic hammer as claimed in claim 13, in which said bit assembly is moveable between two positions, the first in which the shaft thereof is wholly within said casing and the second in which a portion of said shaft extends from the casing end.